use_threads set to True for openMp

[weiyuan-jiang]

If use_threads set to true, there would be some issues:

1. the call ESMF_GridCompGet(gc, grid=grid) crashes immediately after the gc is created here
2. The im_world cannot be retrieved by the call MAPL_GridGet(grid, globalCellCountPerDim=dims) where grid is created under OpenMP condition

@aoloso